Postfix emails are not reaching GMail

You sure it's not winding up in your spam folder? Do you have proper SPF records set? Do you have DKIM configured?

Not in Spam.

I followed the guide to install Postfix Gateway on Debian 6 some months ago, and it worked normally until few days ago.

I guess I haven't setup any SPF record nor DKIM, but I think that if Google can't verify the email it would be on the Spam and not just disappeared, so it should be another issue.

I just tried the mail forwarding from a Hotmail account and it reached the GMail inbox without problems. I think that Gmail discards repeated emails or something like that, and now I cannot send a test email from the same account that will receive it.

I will check what happens with the incoming emails. Thanks

Yes, if you send a message from Gmail that gets forwarded back, it won't show up in your Gmail inbox. Here is one prior post describing this behavior; if you search the forum you may find more discussion about it.

My recollection is that the solution is to use a different webmail provider for testing, or two separate Gmail accounts.